In a gerotor motor, the outer ring’s gear teeth remain stationary while fluid flow turns the internal rotor. This drawing is of a six-pointed gerotor assembly. To see a motor’s internal components in action, view the YouTube video, Motion Study of the Gerotor Motor at http://www.youtube.com/watch?v=iooA0mJzEIE.
Machine Design has always been one of the best engineering teaching magazines out there and this article on hydraulic motors is an example of why. Informative and elegant graphics, straight forward, intelligent and direct (without dumbing down) explanatory prose. OK it’s about hydraulic motors but it’s cool, neat, etc, especially in this age of the maker revolution.